Abstract: A method for producing high-tenacity polypropylene fibers with a tenacity greater than 6 cN/dtex and an elongation of less than 40%. To produce as much as possible fibers of a very fine denier, the fiber strands are spun in a first step at a low melting point of less than 250° C., and are withdrawn at a relatively low withdrawal speed of less than 100 m/min., while being simultaneously cooled by a gaseous cooling medium. Subsequently, the fiber strands undergo drawing in at least three draw zones with a total draw ratio greater than 4:1. In this process, the fiber strands are partially drawn in the first draw zone to at least 70% of the total draw. After having been drawn, the fiber strands are cut to a predetermined fiber length.

Abstract: The invention relates to a process for producing sheath-core staple fibers with a three-dimensional crimp and to a sheath-core staple fiber of this type. In this case, the fiber is extruded with a symmetrical sheath-core arrangement consisting of two different polymer melts with a first polymer component for the core and with a second polymer component for the sheath. In order to generate an as far as possible intensive three-dimensional crimp in the fiber, the cooling of the fiber takes place by means of a sharp cooling air stream with a blowing air velocity of at least 3 m/sec., after the combining of the fibers into a tow the multistage treatment in a fiber line taking place under a maximum temperature load which lies below the glass transition temperature of the second polymer component in the sheath of the fiber. A high degree of three-dimensional crimping can consequently be achieved after the multistage treatment and before the cutting of the fiber.

Abstract: A method for producing high-tenacity polypropylene fibers with a tenacity greater than 6 cN/dtex and an elongation of less than 40%. To produce as much as possible fibers of a very fine denier, the fiber strands are spun in a first step at a low melting point of less than 250° C., and are withdrawn at a relatively low withdrawal speed of less than 100 m/min., while being simultaneously cooled by a gaseous cooling medium. Subsequently, the fiber strands undergo drawing in at least three draw zones with a total draw ratio greater than 4:1. In this process, the fiber strands are partially drawn in the first draw zone to at least 70% of the total draw. After having been drawn, the fiber strands are cut to a predetermined fiber length.